This invention relates to a method and apparatus for conducting chromatographic analysis.
Presently, there are a number of chromatographic methods for isolating organic compounds from complex mixtures of organic compounds in order to identify the type and amounts of the constituents of the mixture. In unidimensional multiple chromatography (UMC), a solution of the organic mixture is resolved with a developing solvent(s) and an absorbent chromatographic material such as alumina and silica gel plate by a normal method wherein the operator does the multiple development by hand. This procedure requires repeated irrigation of the chromatographic material with the solution followed by evaporation of the solvent to leave the solute on the plate. In order to effect separation of mixtures of closely related organic compounds into the constituents of the mixture, long periods of manual work, e.g., up to about 30 hours is required, particularly when a solvent of a weak strength is utilized which comprises effective separation. This procedure is difficult to apply for the routine procedure and is therefore undesirable.
A second method comprises programmed multiple development (PMD) wherein a sandwhich of a chromatographic material formed of silica gel TLC plate is placed in continuous contact with a reservoir of the solution and the solvent is continuously evaporated by exposing the chromatographic material containing the solution to infrared radiation. This method is undesirable since the infrared radiation increases undesirable oxidation and thermal degradation of labile compounds. This, in turn, results in inaccuracy in determining the presence of certain compounds in the sample tested and, if so, the amounts of these compounds in the sample. In addition, heating leads to increased rates of evaporation from the solvent reservoir in which the chromatographic plate is placed. This increased evaporation also leads to inaccuracies since the effect is to reduce the vertical position the solute normally would have on the chromatographic strip. Alternatively, PMD can be conducted by passing a dry inert gas over the chromatographic plate to increase the rate of solvent evaporation. However, uniform evaporation from the plate is difficult with this method which leads to the reduction in a uniform chromatographic resolution of the solute and this method also introduces difficulty in controlling the level of the solvent reservoir.
Alternatively, organic mixtures can be analyzed by gas chromatography. While this method yields efficient discrimination of the constituents of the mixture, it is undesirable for the purpose of the routine application since the required apparatus is extremely expensive.
Accordingly, it would be highly desirable to provide a chromatographic method for analyzing organic mixtures which is at least as accurate as gas chromatographic procedures, does not require manual labor throughout the process and which does not require expensive apparatus.